1. Field of the Invention
The present invention relates generally to a common rail in an accumulator fuel injection system of a diesel internal combustion engine or a gasoline internal combustion engine.
2. Description of the Related Art
The common rail of this type is constructed of an elongated cylindrical main pipe rails having a flow path for storing pressurized fuel therein in many cases. However, as shown in FIG. 3 and FIG. 4, there is also a common rail constructed of a short cylindrical main pipe. The common rail of this type includes a main pipe rail 10 constructed of a short cylindrical body having a ceiling wall 11 of substantially flat shape or spherical shape (not shown) and boss portions 12 at a plurality of locations on a side wall, and a bottom wall 13 screwed into the main pipe rail 10. The common rail of this type is formed with a flow path 14 shaped like a flat space within the cylindrical body 10, a branch hole 15 formed in each of the boss portions 12, the branch hole 15 communicating with the flow path 14 of the main pipe rail 10 and having a pressure receiving bearing surface 16 opening outward, a male thread 12-1 formed on the outer periphery of each of the boss portions so that a supply pipe or an injection pipe (not shown) can be screwed thereon, and securing bracket 17 formed integrally with the main pipe rail 10 on the side of the bottom wall 13 at the other end.
However, since the common rail in the related art shown in FIG. 3 and FIG. 4 is manufactured as a product by fabricating a specific material by die forging and then machining a flow path, a branch joint, and a bracket, it has following disadvantages.
Since the specific material is formed by integral molding by die forging, a mold of high strength and high price is required. Since such specific material has to be finished by machining, long processing time is required. Since the material has to be heated up to a high temperature for improving moldability, energy for heating is required. Since tough oxide scale is generated due to hot processing, post processing, such as shot blast or acid cleaning, is required. In addition, high manufacturing cost is required.